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lightcraft/docs/file-format-parity.md
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Andrew FrahnandClaude Opus 5.5 a1d7c488f8 LR-EXP-RENDERDNG: Render to DNG export format (linear float DNG of the rendered photo) 
New export format `rendereddng` (export dialog: Format DNG, "DNG of: Rendered
photo"; `app.export`; MCP export tool): the rendered photo, with the edit,
crop, size, output sharpening and watermark baked in, written by the new
`lightcraft_raw::write_rendered_dng` as a LinearRaw DNG of 16-bit float Deflate
tiles in the export colour space. ColorMatrix1 (XYZ -> space), ForwardMatrix1
(space -> XYZ D50), a neutral AsShotNeutral and an identity ProfileToneCurve
make raw converters show it as rendered. HDR edits keep highlights above white.
Bad input (wrong sample count, zero or huge sizes, NaN/inf, out of half-float
range) gives an error or is clamped, never a panic.

Also fixes the Rust 1.99 clippy lint chunks_exact_to_as_chunks in
pipeline/spots.rs that fails `cargo xtask ci` on main.

Sources: Adobe DNG Specification 1.4+ (LinearRaw, ColorMatrix/ForwardMatrix,
ProfileToneCurve); own design.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
2026-10-12 04:33:12 +11:00

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# File format parity
> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-12 · **Change:** minor (Render to DNG as an export format) · **Target:** Adobe Lightroom Classic 15.5 / Lightroom 9.6
Every format Lightroom reads or writes, with our support, fidelity and tests. Camera raw formats are
deep enough to have their own document: [raw-parity.md](raw-parity.md).
**How measured:** the target's document types come from the installed Lightroom 9.6
`Info.plist` (`CFBundleDocumentTypes`: catalog `mcat`, `xmp`, toolkit / module / library bundles, and
the raw-and-image list: jpg, tif, dng, heic and 27 raw extensions) plus Lightroom Classic's documented
import and export formats. Ours come from `crates/codecs/src/sniff.rs`, `crates/codecs/src/encode.rs`,
`crates/engine/src/export.rs`, `crates/engine/src/import.rs` and the tests named below.
## Images (non-raw)
| Format | Target reads | Target writes | LightCraft reads | LightCraft writes | Notes / tests |
|---|---|---|---|---|---|
| JPEG | ✅ | ✅ | ✅ (parallel decoder, ICC, EXIF orientation) | ✅ quality, size limit, ICC, metadata | `crates/codecs/src/jpeg.rs`, export tests |
| TIFF | ✅ 8/16/32-bit | ✅ 8/16-bit, LZW/ZIP | ✅ 1–64-bit integer, 16–64-bit float, bilevel, CCITT fax, WhiteIsZero | ✅ 8/16-bit, 32-bit float linear, none / LZW / ZIP | `crates/tiff`, `crates/codecs/src/tiff_codec.rs` |
| PNG | ✅ | ✅ | ✅ | ✅ | |
| PSD / PSB | ✅ (maximized-compatibility composite) | ✅ (Classic: PSD export, edit-in round trip) | ✅ merged composite | ⬜ (external-editor round trip writes 16-bit TIFF) | `crates/codecs/src/psd.rs` |
| HEIC / HEIF | ✅ | ⬜ (Classic) / HDR only | ✅ in every release build (`crates/heif`, heic-rs) | ⬜ | `heif` feature on by packaging scripts |
| AVIF | ✅ | ✅ (HDR) | ⬜ recognised, not decoded (no permissive pure-Rust AV1 decoder) | ✅ 8/10-bit, PQ HDR | |
| JPEG XL | ✅ | ✅ | ✅ (`jxl-oxide`) incl. DNG 1.7 JXL tiles | ✅ lossy / lossless, 8/16-bit, PQ HDR (`jixel`, native only; ⬜ web) | `crates/engine/src/tests_export.rs` |
| WebP | not in its document types | ⬜ | ✅ | ✅ | beyond target |
| GIF, BMP | ⬜ | ⬜ | ✅ | ⬜ | beyond target |
| DNG (from raw) | ✅ | ✅ incl. lossy, embedded original | ✅ | ✅ uncompressed or LJ92; ⬜ lossy DNG, embedded original | `crates/raw/src/dngwrite.rs` |
| Render to DNG (15.5) | — | ✅ | — | 🟡 export format "Rendered DNG" (linear float DNG, edit baked in); not yet added to the catalog | `crates/raw/src/dngwrite.rs` (`write_rendered_dng`) |
| Original + sidecar | — | ✅ | — | ✅ | |
| HDR gain map JPEG (ISO 21496-1) | ✅ | ✅ | ✅ (gain map read) | ✅ | `crates/codecs/src/gainmap.rs` |
| PQ / HLG HDR | ✅ | ✅ AVIF, JXL, TIFF | — | 🟡 PQ AVIF, PQ JPEG XL, float TIFF; no HLG | |
| Contact sheet / print PDF | — | ✅ (Print module: PDF / JPEG / printer) | — | 🟡 paginated contact-sheet PDF (A4 / Letter, 150 dpi, sRGB) | `crates/engine/src/contact_sheet.rs` |
| Video (MP4, MOV, AVCHD…) | ✅ playback, trim, edit | ✅ export | 🟡 catalogued (kind, duration) | ⬜ | see video gap |
## Colour spaces and profiles
| Feature | Target | LightCraft |
|---|---|---|
| Export colour spaces | sRGB, Adobe RGB, Display P3, ProPhoto, Rec.2020, custom ICC | ✅ sRGB, Display P3, Adobe RGB-compatible, ProPhoto, Rec.2020 with gamut mapping (CPU and GPU), embedded ICC; ⬜ custom ICC output profiles; AVIF stays sRGB |
| Input ICC (JPEG / TIFF / PNG) | ✅ | ✅ matrix / TRC and LUT profiles (moxcms) |
| Soft proofing with printer profiles | ✅ | 🟡 |
## Metadata, sidecars, presets and catalogs
| Format | Target | LightCraft | Notes |
|---|---|---|---|
| XMP sidecars (`crs:` develop settings, ratings, keywords, regions) | read / write | ✅ read / write, manual (⌘S) and automatic | [xmp-interop.md](xmp-interop.md) |
| EXIF / IPTC / XMP embedded on export | ✅ | ✅ with metadata filters | `crates/meta` |
| Develop presets `.xmp` | ✅ | ✅ import (mapping of supported settings) | |
| Legacy presets `.lrtemplate` | ✅ (converted) | ✅ import | |
| Camera / creative profiles (`.dcp`, `.xmp` profiles) | ✅ | ⬜ deliberately (Adobe profile formats are never used); `.cube` LUT profiles ✅ | |
| Lens profiles `.lcp` | ✅ | ⬜ deliberately | |
| Other apps' presets | — | ✅ Luminar `.lmp` / `.mplumpack`, `.zip` bundles | beyond target |
| Lightroom Classic catalog `.lrcat` | native | 🟡 import (ratings, flags, labels, keywords, collections, virtual copies, supported develop settings; read-only pure-Rust SQLite incl. WAL) | [lightroom-catalog-import.md](lightroom-catalog-import.md) |
| Lightroom (cloud) library `.lrlibrary` | native | ⬜ | cloud library format, local cache only |
| Write back to `.lrcat` | native | ⬜ (one-way migration by design) | |
| Keyword lists (text) | import / export | ✅ | |
| GPX track logs | ✅ | ✅ | `crates/meta/src/gpx.rs` |
| Export presets, metadata presets, filename templates | ✅ (`.lrtemplate`) | ✅ own JSON | not interchangeable |
| Lightroom plug-ins (`.lrplugin`, `.lrdevplugin`) | ✅ | ⬜ | see ecosystem in [target-app-parity.md](target-app-parity.md) |
## Scores
| Part | Weight | Ready for real work | Kind |
|---|---:|---:|---|
| Standard image import / export | 35% | ~85% | estimated (table above; missing: AVIF read, PSD write, lossy DNG) |
| Sidecars, metadata, presets | 25% | ~85% | estimated |
| Lightroom catalog migration | 25% | ~50% | estimated (one-way, approximate rendering of unsupported settings) |
| HDR, print, video output | 15% | ~35% | estimated |
| **Non-raw file formats** | 100% | **~70%** | estimated; raw is in [raw-parity.md](raw-parity.md) (~50%) |
Remaining: **26–47 h** (AVIF decode 8–15 h if a permissive decoder is written or found; PSD write 4–8 h; lossy DNG and Render to DNG 4–8 h; HLG 3–5 h; catalog import depth 8–12 h).
## Revision history
| Date | Change | Summary |
|---|---|---|
| 2026-10-10 | major | Created from the code and the installed Lightroom's document types |
| 2026-10-10 | minor | JPEG XL export (#247): JXL write ✅ (native only), PQ JPEG XL HDR |
| 2026-10-12 | minor | Render to DNG: "Rendered DNG" export format (linear 16-bit float DNG of the rendered photo) |
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